The present invention relates to integrated circuits and their manufacture. The present invention is illustrated in an example with regard to plasma etching, and more particularly to plasma etching of resist strippers in semiconductor processing. But it will be recognized that the invention has a wider range of applicability in other technologies such as flat panel displays, large area substrate processing, and the like. Merely by way of example, the invention may be applied in plasma etching of materials such as silicon, silicon dioxide, silicon nitride, polysilicon, photoresist, polyimide, tungsten, among others.
Industry utilizes or has proposed several techniques for plasma etching. One such method is conventional chemical gas phase dry etching. Conventional chemical gas phase dry etching relies upon a reaction between a neutral gas phase species and a surface material layer, typically for removal. The reaction generally forms volatile products with the surface material layer for its removal. In such method, the neutral gas phase species may be formed by way of a plasma discharge.
A limitation with the conventional plasma etching technique is obtaining and maintaining etching uniformity within selected predetermined limits. In fact, the conventional technique for obtaining and maintaining uniform etching relies upon a "trial and error" process. The trial and error process often cannot anticipate the effects of parameter changes for actual wafer production. Accordingly, the conventional technique for obtaining and maintaining etching uniformity is often costly, laborious, and difficult to achieve.
Another limitation with the conventional plasma etching technique is reaction rates between the etching species and the etched material are often not available. Accordingly, it is often impossible to anticipate actual etch rates from reaction rate constants since no accurate reaction rate constants are available. In fact, conventional techniques require the actual construction and operation of an etching apparatus to obtain accurate etch rates. Full scale prototype equipment and the use of actual semiconductor wafers are often required, thereby being an expensive and time consuming process.
From the above it is seen that a method and apparatus of etching semiconductor wafers that is easy, reliable, faster, predictable, and cost effective is often desired.